Exercise Physiology and Effects of Exercise on Body Systems
This section covers exercise physiology and the effects of exercise on body systems. The exam tests acute responses, long-term training adaptations and correct use of terms such as stroke volume and cardiac output.
Acute responses
During exercise, heart rate rises, stroke volume rises, and cardiac output increases. Breathing rate and tidal volume increase. Blood flow is redistributed to working muscles and skin, sweating increases for cooling, and lactic acid can accumulate when intensity exceeds aerobic capacity.
Chronic adaptations
Regular endurance training lowers resting heart rate and raises stroke volume, capillary density and mitochondrial density. Vital capacity and respiratory efficiency improve. Resistance training increases muscle strength and size, and weight-bearing activity supports bone density. Training also improves insulin sensitivity and blood lipid profile.
Key relationships
Cardiac output = heart rate × stroke volume. Maximum heart rate is often estimated as 220 minus age, but this is only an estimate.
Worked example
At rest, heart rate is 70 beats per minute and stroke volume is 70 mL. Cardiac output = 70 × 70 = 4,900 mL per minute, or 4.9 L/min. During exercise, heart rate is 140 and stroke volume is 100 mL, so cardiac output = 14,000 mL/min, or 14 L/min. Reasoning: both rate and volume contribute; the rise is not due to heart rate alone.
Traps
Do not say trained people have a higher resting heart rate. Do not confuse stroke volume with cardiac output. Do not treat 220 minus age as a measured value. Do not claim exercise reduces maximum cardiac output.